Seed dispersal effectiveness in a plant–lizard interaction and its consequences for plant regeneration after disperser loss

Abstract

Mutualistic disruptions, such as those promoted by the loss of seed dispersers, can have negative effects on the plant regeneration of those species that strongly depend upon them. In order to adequately assess how plant communities are affected by such disruptions, we need to know the importance of the dispersal phase, both in its quantitative and qualitative components. We examined this in the narrow interaction between the shrub Daphne rodriguezii and its (only) disperser, the lizard Podarcis lilfordi. We quantified fruit removal and the effect of fruit/seed-size selection, seed treatment in the disperser's guts and seed deposition patterns on seedling emergence and survival. In the only locality in which lizards persist, they removed most fruits and showed preference for larger ones in one of the two study years. Seed treatment in lizard's guts had no effect on germination, although it tended to reduce the effect of seed size on germination (differences between large vs. small seeds in seed germination were higher for non-ingested seeds). Probability of seedling emergence, but not survival, was higher in the locality with lizards. Dispersed seeds under heterospecific shrubs showed higher seedling survival than those under conspecifics in all localities, especially the year with higher rainfall. Our findings support that the movement of seeds to nurse shrubs by lizards is the most important component of the seed dispersal process in the only remaining locality where both species coexist.

Herbivory by Lizards

“…Once again, regarding the work of Rodríguez-Pérez and Traveset [21], it was observed that seedlings of seeds deposited under the mother plant had lower survival rates compared to the seeds dispersed. Accordingly, even though the passage through the digestive tract of lizards does not significantly increase the germination rate, the deposition pattern of seeds increases the viability of seedlings survival.…”

“…Rodríguez-Pérez and Traveset [21] studied the interaction between Daphne rodriguezii, an endemic shrub from Menorca Island (in Spain), with the lizard Podarcis lilfordi (Günther, 1874), which is its disperser. In such study the seeds size was not an important factor for the selection of fruits, because seeds are not predictors of the amount of pulp mass.…”

“…Quantitative factors depend on the number of seeds consumed, while the qualitative ones depend on the location in which the seed is deposited and the effect of the passage through the digestive tract on seed germination [33][34][35]. The treatment that the seeds receive when they are consumed directly influences the capacity and the speed of germination [21]. In the same way that the distribution pattern of seeds on the microhabitats is a crucial aspect of the dispersion quality [36].…”

“…Information on seed dispersal by lizards are known for: geckos in New Zealand islands [24,26]; lizards in various environments in Brazil [31,37], in the Mexico (Benítez-Malvido et al), in island of the Western Mediterranean [21,38] and iguanas in the Galapagos Islands [39] and dry forests of Costa Rica [40].…”

“…Rodríguez-Pérez and Traveset [21], in a paper about the interaction of the bush D. rodriguezii and its disperser, namely, the lizard P. lilfordi, stated that the passage through the digestive tract neither increased nor decreased the germination capacity. Nevertheless, the passage through the digestive tract appeared to have caused a reduction in size of the seed, with an action on the coating thickness.…”